Glass has been widely used as a material of containers or vessels for seasonings, oils, beer, wines, refrigerant drinks such as carbonated drinks, cosmetics and detergents. While glass vessels are excellent in their gas-barrier property, because of their relatively high costs of manufacture they are normally recovered after service and re-used. Glass vessels, however, pose problems in that costs of transportation are expensive due to their considerably heavy weight and that they are liable to break and inconvenient to handle.
To eliminate the above-mentioned problems involved in glass vessels, plastic containers or vessels have become employed in place of glass vessels. Depending upon the nature of materials to be stored in plastic vessels, various plastics are employed to manufacture the vessels. Among others, because of its good transparency and gas-barrier property, polyethylene terephthalate has been adopted as a material of vessels for seasonings, refrigerant drinks, detergents and cosmetics.
However, in the case of vessels for beer and carbonated drinks where a requirement for the gas-barrier property is the most severe, polyethylene terephthalate is not necessarily satisfactory in this respect, and in consequence, it has been necessary to prepare thick wall vessels to meet the requirement.
On the other hand aliphatic polyamides such as nylon 6 and nylon 66 exhibit a better gas-barrier property in dry state than polyethylene terephthalate. Such polyamides normally have a water absorption on the order of 10%, and pose a problem in that when wet their gas-barrier property is worse than that of polyethylene terephthalate. To improve the water absorbing property of aliphatic polyamides, Japanese Patent Laid-Open Publication No. 60-195126 (1985) discloses crystalline polyamides containing cyclic hydrocarbon groups. Although the disclosed polyamides have an excellent gas-barrier property, resins having a further improved gas-barrier property are desired in the art.